Abstract
In shape-memory polymers, changes in shape are mostly induced by heating, and exceeding a specific switching temperature, Tswitch.
If polymers cannot be warmed up by heat transfer using a hot liquid or gaseous medium, noncontact triggering will be required.
In this article, the magnetically induced shape-memory effect of
composites from magnetic nanoparticles and thermoplastic shapememory polymers is introduced. A polyetherurethane (TFX) and a biodegradable multiblock copolymer (PDC) with poly(p-dioxanone) as hard segment and poly(-caprolactone) as soft segment
were investigated as matrix component. Nanoparticles consisting
of an iron(III)oxide core in a silica matrix could be processed into both polymers. A homogeneous particle distribution in TFX could be shown. Compounds have suitable elastic and thermal properties for the shape-memory functionalization. Temporary shapes of TFX compounds were obtained by elongating at increased temperature
and subsequent cooling under constant stress. Cold-drawing of
PDC compounds at 25°C resulted in temporary fixation of the mechanical deformation by 50–60%. The shape-memory effect of
both composite systems could be induced by inductive heating in
an alternating magnetic field (f 258 kHz; H 30 kAm1). The
maximum temperatures achievable by inductive heating in a specific
magnetic field depend on sample geometry and nanoparticle
content. Shape recovery rates of composites resulting from magnetic
triggering are comparable to those obtained by increasing the environmental temperature.
DOI Link to Publication